1. Field of the Invention
The present invention relates to a low noise blower for a heat exchanger.
A propeller fan is usually used for blowing air for performing a heat exchange operation in appliances such as a refrigerator, an outdoor device of an air conditioner, a computer and the like.
Air at an exit side in the propeller fan, unlike that of a genuine axial fan, is discharged at a predetermined angle relative to the axis of rotation of the propeller.
Furthermore, because the propeller fan is mainly used for an appliance having a predetermined circulation route of the air, a shroud or bell mouth is installed around a periphery of the propeller fan in order to define an air circulation route at the exit of the fan and to improve the performance of the fan.
FIGS. 1 and 2 are drawings for illustrating a conventional blower having a propeller fan 10 and a bell mouth 20 wherein FIG. 1 is a front view and FIG. 2 is a side sectional view.
As described above, the conventional blower comprises: a motor 30 for receiving power from an electrical power source; a propeller fan 10 for being rotated by the motor 30; a bell mouth 20 for encompassing the periphery of the propeller fan 10; and a bracket 40 for supporting the motor 30 and fixed to the bell mouth 20. The fan 10 includes a hub 12 and an array of radial blades 14.
Accordingly, when the motor 30 is activated, the propeller fan 10 starts rotating and creates an air flow F.
When the propeller fan 10 is rotated, the air at an entrance of the bell mouth 20 (left side thereof in FIG. 2) is increased in pressure by centrifugal force and buoyancy to thereby be discharged toward an exit (to the right in FIG. 2).
At this time, the sound (blade rotating sound) of the fan 10 and an air flow operational noise, including air noise of a broad band, emanate from the blower.
Meanwhile, one of the most important factors in determining the performance and noise of the blower is the design of the propeller fan 10, along with the design of the bell mouth 20.
In other words, in order to obtain high efficiency and low noise operation of the propeller fan 10, the construction of the bell mouth 20 with respect to an outer diameter and a width thereof are major design factors, along with the design of the fan blades.
Furthermore, an assembled structure of the fan 10 to the bell mouth 20 is an important factor in determining the performance and noise reduction of the blower.
The above drawing illustrates the important design factors of the fan 10 and bell mouth 20.
In other words, the outer diameter Df and the width Wf of each blade are important factors in designing the fan 10, and an inner diameter Db, a width Wb and a curvature Rb of the bell mouth 20 are illustrated as important factors in designing the bell mouth 20. The curvature Rb is between axial and radial sections 22, 24 of the bell mouth.
Furthermore, a distance l between starting points (i.e., upstream ends) 50, 60 of the fan 10 and the bell mouth 20 is illustrated in the drawing as an important factor in determining the performance and the noise of the blower.
The performance and noise of the blower can be changed by varying the design factors thus described. However, heretofore there has been no optimization of the inner diameter Db, width Wb and the curvature Rb of the bell mouth 20 the outer diameter Df and the width Wf of the propeller fan 10, so a considerable amount of air flow loss generated during the operation of the blower has occurred.
Furthermore, the assembled structure of the fan 10 to the bell mouth 20 plays an important role in determining the performance and the noise of the blower, and an optimum relation thereof has not been established so far, which has limited realization of high performance and low noise of the blower.
In other words, the axial distance l between end points on the fan 10 and the bell mouth 20 is an important factor in determining the performance and the noise of the blower and not heretofore been clearly defined, which has thereby caused a decreased efficiency and increased operational noise.
The performance and noise such as the blowing quantity and the like can be measured by experimentally.
In the case of a conventional blower, the blowing quantity (air flow) is measured as being less than approximately 1.9338.times.10 m.sup.3 /sec and the noise is measured as more than approximately 26.1 dB(A).